In biochemical experiments, samples containing molecules such as DNA with various lengths are sometimes separated by electrophoresis. By electrophoresis, molecules such as DNA or proteins migrate on a gel by the application of an electric field, thereby being separated and established as bands according to their molecular weights. A range where bands have migrated from the same initial migration point is defined as a lane.
FIG. 19 is a schematic diagram of an electrophoresis device. Hereinafter, separation of DNA molecules will be described as an example. The electrophoresis device 1903 is provided with a negative (−) electrode 1904 and a positive (+) electrode 1905, which are connected to a power source 1901 via a conductor 1902. A sample is put into a sample inlet 1906 on the (−) electrode 1904 side, and a voltage is applied. As a result, negatively-charged DNA molecules are electrically pulled and thus migrate from the (−) electrode 1904 side toward the (+) electrode 1905 side. According to the difference of the molecular weights, the molecules are separated into a DNA molecule 1908 of a larger molecular weight, a DNA molecule 1909 of a middle molecular weight and a DNA molecule 1910 of a small molecular weight. The path where these DNA molecules have migrated is a lane 1915. The states of the DNA molecules separated on the lane 1915 can be observed with a CCD camera or the like, and may be analyzed by image processing.
For image processing, the DNA molecules present on the lane 1915 are established as bands on an image of the post-migration DNA molecules. The bands can be established automatically by reading the brightness of pixels on the lane, integrating the brightness in the migration direction 1907 from the sample inlet 1906 and in the direction perpendicular to the migration direction 1907, and detecting a peak position 1917 from a generated spectrum 1916. Then, lines perpendicular to the migration direction 1907 are drawn on the lane 1915 at positions corresponding to the peak positions, thereby setting a band 1911 (the DNA molecule 1908), a band 1913 (the DNA molecule 1909) and a band 1914 (the DNA molecule 1910).
When the lane 1915 is contaminated by dust 1919, the dust 1919 will appear as a peak 1918 on the spectrum 1916, and could be mistakenly detected as a band 1912. In order to carry out the experiment, the setting of the error band 1912 must be cleared. For this purpose, the image processor is provided with a band selecting function. In general, in order to select a band, an operator inputs a band selecting command with a pointing unit such as a mouse looking at the bands displayed on the image display unit. When the band to be selected is too small or too narrow to be selected with the pointing unit, a predetermined range of the band displaying region is enlarged to ease the selection.
In order to select a band on the image with the pointing unit such as a mouse according to the band selecting function of a conventional image processor, the cursor of the pointing unit must accurately point the band of interest on the lane displayed on the image display unit. Furthermore, when the band of interest is very close to another band or is in the middle of a group of gathering bands, the band regions overlapping in the image makes it difficult or impossible to designate the band of interest with the pointing unit.
In view of such problems of an image processor for processing electrophoresis image data, the present invention has an objective of providing a device and method for simply and efficiently selecting and displaying a band present on a lane.